The Big Five was a series of biological weapons developed by the United States Army Chemical Corps' Special Operations Division (SOD) at Fort Detrick Biological Warfare Laboratory (BWL) for use by special forces.
These weapons were developed in the 1950s and 1960s, and were eventually destroyed when the United States unilaterally ended its offensive biological warfare program.
The weapons were - M1 Biodart (E1) A 7.62mm rifle cartridge with a sabot surrounding a flechette with exterior grooves filled with either botulinum toxin A (XR), saxitoxin (TZ), or possibly a combination of the two.
M5 Depositor (E44) A metal can that would expel a quantity of dry-type from the side of a road to work as an anti-convoy device from secondary aerosols (kick-up).
M32 Disperser Using a pressurized gas bottle, regulator, heater, and timer, the M32 was a man-pack weapon for pre-emplacement upwind of a target.